First and third links clearly state that these students are volunteers, and also a fairly small amount of them. (Also doesn’t seem like trolling necessarily)
Second link seems promising, but it offers almost no details, and its source is HaAretz, an Israeli publication which I personally don’t trust (also the source article is behind a paywall).
Last link is about a private company and seems only slightly related.
Not really strong evidence of Israel running “Russian troll factories”.